1. Field of the Invention
The present invention relates to a fluid-operated press and, more particularly, to a fluid-operated press having a frame structure for a precision work and being suitable specifically for a plastic working.
2. Description of the Prior Arts
Such a fluid-operated press has been known as having a crosshead, a bed, four upstanding posts extending between the crosshead and the bed, and a slider disposed between the crosshead and the bed and slidably fitted on the upstanding posts so as to slide along the posts, wherein the upstanding posts are of such a rectangular arrangement that the axes of the posts extend vertically through respective corners of a rectangular plane. The fluid-operated press of this type in which the upstanding posts serve as members for guiding the sliding movement of the slider has an advantage that a stable and smooth guide for the sliding movement of the slider can be effected with a comparatively simple construction. The frame structure of this type of press, however, has a small lateral rigidity, so that undesirable distortion or displacement of the slider, such as inclination or skew of the slider with respect to the plane of surface of the bed, is caused during the operation of the press. For this reason, it has been impossible to maintain with high precision a preferable positional relationship between the slider and the bed.
A typical example of known fluid-operated press improved to provide a high rigidity and hence to maintain with high precision the preferable positional relationship between the slider and the bed includes an upright wall structure having box-like upright walls completely surrounding the entire periphery of each upstanding post. Unfortunately, however, this improved fluid-operated press cannot easily effects a smooth and stable guide for the sliding movement of the slider, and hence a complicated and expensive construction is required for maintaining with high precision the preferable positional relationship between the slider and the bed.